Quantitative Compositional Mapping of Core−Shell Polymer Microspheres by Soft X-ray Spectromicroscopy

Abstract

Core-shell polymer microspheres have been prepared by a two-step precipitation polymerization. These microspheres consist of 3.2 µm polydivinylbenzene-55 (DVB55) cores coated with ∼0.4-0.9 µm wide shells composed of poly(DVB55-co-EDMA), a random copolymer of DVB55 and ethylene glycol dimethyl acrylate (EDMA). The chemical composition, core-shell morphology, and porosity of these structured microspheres have been studied quantitatively with scanning transmission X-ray microscopy (STXM) at a spatial resolution of 100 nm. Images recorded at selected energies through the C 1s absorption region were analyzed using singular value decomposition to obtain quantitative maps of the DVB55 and EDMA components. The EDMA concentration in the shell determined by STXM was found to be in good agreement with that predicted from the comonomer composition over the range of 10-90% EDMA. The precision of chemical quantification at high spatial resolution is shown to be adequate for STXM to be useful in guiding the development of structured polymeric systems for particular applications.

Facile synthesis of silica/polymer hybrid microspheres and hollow polymer microspheres

“…The residual reactive vinyl groups on the surface of polyDVB cores were essential to obtain monodisperse coreeshell functional microspheres by twostage precipitation polymerization [38], in which the newly formed oligomers and monomers were captured by these reactive vinyl groups in the absence of any second-initiated small particles during the second-stage polymerization. In the present work, the MPS-modified silica particles with vinyl groups on the surface were used as seeds in the second-stage distillation precipitation polymerization for the growth of the shell-layer to afford monodisperse silica/polyDVB and silica/ polyEGDMA coreeshell hybrid microspheres as shown in Scheme 1.…”

“…The essential role of the vinyl groups on the surface of MPS-modified silica cores was confirmed further by the formation of the separated-irregular particles (TEM image not shown here) in the presence of silica particles as seeds for the polymerization of DVB and EGDMA, in which neither DVB nor EGDMA can be encapsulated onto the silica core due to its hydrophobic nature lacking efficient interaction with the silica particles. It was reported that the residual vinyl groups located on the surface of polyDVB microspheres favored the capture of the radical oligomers and monomers from the solution to grow the particles in precipitation polymerization [38] and distillation precipitation polymerization [29].…”

Qualitative detection of single submicron and nanoparticles in human skin by scanning transmission x-ray microscopy

“…[20][21][22] Various studies devoted to materials sciences ͑e.g., on hollow microcapsules and core-shell polymer micro-spheres͒ have also made use of x-ray microscopy. [23][24][25][26] In STXM, high-brilliance synchrotron radiation is tightly focused ͑40 nm͒, and the sample is raster scanned while recording the intensity of transmitted x-rays in order to produce a two-dimensional image. Besides from spatial resolution, x-ray microscopy also provides chemical contrast, which is a result of strong variations of the absorption cross section in core level absorption.…”

A facile route to poly(divinylbenzene) hollow microspheres with pyridyl group on the interior surface

“…The essential role of the vinyl groups were confirmed further by the formation of irregular particles in the presence of PMAA microspheres as seeds for the polymerization of DVB without the aid of VPy (TEM micrograph not shown here). It was reported that the residual vinyl groups located on the surface of polydivinylbenzene (PDVB) microspheres favored the capture of the radical oligomers and monomers from the solution to grow the particles in precipitation polymerization [26]. The TEM micrographs of the resultant PMAA@PDVB microspheres with different thickness of shell layer are shown in Fig.…”